More stubs and instructions for arm64.

runtime/vm/unit_test.cc

Index: runtime/vm/unit_test.cc
===================================================================
--- runtime/vm/unit_test.cc	(revision 35551)
+++ runtime/vm/unit_test.cc	(working copy)
@@ -48,8 +48,6 @@
   }
 }
 
-// TODO(zra): Remove when tests that need these functions are ready to enable.
-#if !defined(TARGET_ARCH_ARM64)
 
 static Dart_Handle LibraryTagHandler(Dart_LibraryTag tag,
                                      Dart_Handle library,
@@ -144,7 +142,6 @@
   return Api::Success();
 }
 
-#endif
 
 void AssemblerTest::Assemble() {
   const String& function_name = String::ZoneHandle(Symbols::New(name_));